This invention relates to reaction vessels and more particularly high temperature reaction vessels having inert metal surfaces.
Many of the component elements, oxides and nitrates used in synthesizing high temperature superconductor (HTS) compounds (and perhaps other classes of compounds) tend to react with most containment vessels during the high temperature processing required to form or sinter the materials. The noble metals are the only materials which remain essentially non-reactive under the required processing conditions. The noble metals (gold and silver) have been shown to protect the HTS compounds during thermal treatment and impart beneficial properties as additives. In achieving the the purity of final HTS product necessary for high transport current, introduction of second phases during heat treatment must be minimized. Difficulty arises, however, when pure silver itself is used as a reaction vessel, as much of the processing must be carried out within 100.degree. C. or so of the silver melting point (960.degree. C.). In this circumstance, which is quite common in the processing of high temperature superconductor (HTS) materials, the crucible softens and sags. This may cause the sample to embed itself or to cause other removal problems Needed in this application is crucible (or other vessel shape) which presents a pure silver surface to the sample during thermal processing while maintaining structural stability near the silver melting temperature.